Add level, experience, money to character sheet.
Add level and experience to player display.
Stop creating fractional money (at least for now).
Clean up talent definitions.
Bugfix: Monsters sometimes couldn't move.
Apparently Actor:block_move calls Actor:attack, which calls Actor:bumpInto, which (in my implementation) always used energy.  As a result, if an actor's direct path was blocked and one of its diagonals had a creature in the way, then it would use energy just by seeing that its path was blocked.
Misc. other bugfixes: improve movement speed checking, check if target is dead before swinging additional weapons.

More test of all of this is needed.
Start adding new enemy (Forest Bat).
Non-persistent levels.  Disallow backtracking.
New talent: Fourth Blessing: Longevity
Add utils.lua methods math.average, math.sum
Fix bugs in experience display in recent work.
Implement Second Blessing: Wealth and Pickpocket.

Supporting work:
Combat.talentPercentage, string.a
Add money_value_multiplier.  Allow money value to be fractional internally.

Unrelated:
Adjust digging speed
Fix bugs in timed_effects.lua